More

On Air Schedule:

Happy Spring!

March 20, 2013 at 8:47 am

Spring began at the vernal equinox at 7:02 this morning! It doesn’t look like it with snow and ice all over the region and it doesn’t feel like spring with the temperatures in the middle 20s. Be extra cautious as you head out to work or school this morning due to the presence of icy areas on steps, sidewalks, driveways, parking lots, etc. Some town streets and country roads are also treacherous. There will be some spells of bright sunshine amidst some migrating patches of clouds along with a few isolated flurries through the day. Temperatures will top out in the upper 30s in Worcester County to near 40 in Boston to the lower 40s southeastern MA but the gusty wind will add some chill to the air.

Yesterday’s storm is churning up over the Canadian Maritimes this morning and pulling a supply of cold air into the Northeast. There are no signs that anyone is going to come down with spring fever in the next couple weeks as an anomalous volatile pattern remains entrenched. There will be several storms in the works over this extended period but it is unclear if any of them will strike New England. Any slight realignment of the steering currents could revise this scenario substantially. The first storm threat occurs later tomorrow and tomorrow night. A potential snowfall here actually will not be created by the storm itself. That rapidly deepening beast will bypass the region but a hangback inverted trough of low pressure curling up over southeastern MA may be the focusing boundary for extra air convergence. This so-called Norlun Trough can result in intense, localized bands of precipitation. It is a mesoscale feature poised underneath a pool of very cold air in the mid and upper levels of the atmosphere. This instability can contribute to some narrow corridors of extremely heavy snow that are difficult to precisely pinpoint. Some of the ingredients necessary for the formation of this restricted event is comprised of a deepening storm at sea, quite cold air aloft and favorable atmospheric spin. Forecasting the intensity and placement of these specialized troughs is extremely challenging and the stakes are high because of the extreme gradient of snowfall. For example, a classic Norlun occurred on March 21, 1992 with the max snow zone over and just south of Portland, ME. In this example, conditions were absolutely perfect for up to 18-24″ of snow in a skinny ribbon along the southern ME coast arching back toward Cape Ann. Much of that amount fell in less than 5 hours! Another great extreme example occurred on February 19, 1993 in a similar pattern that cranked out 20″ over Chatham in about 4-5 hours! There is a similar setup in the works for late tomorrow but accurately predicting the position and productivity of the axis of action is not easy. It could blossom just offshore and nobody gets the heavy snow. For now, it appears that southeastern MA and Cape Cod have the best shot of receiving a few to several inches of snow but keep in mind that these are tricky troughs to forecast. Predicting excessive snows in a mesoscale environment has big bust potential.

Looking ahead, the passage of a trough on Friday suggests that there will be varying amounts of clouds and sunshine with a risk of a few scattered snow showers. Then over the weekend, there will be somewhat drier and more stable air resulting in sunnier conditions and temperatures closer to the average for later March. There will be a gusty wind on Saturday with less wind on Sunday. Beyond that, the next storm emerging from the lower Midwest might make a run at New England on Monday. Currently, there are mixed signals on the precise path of this system with a lean toward the storm just missing our region on its way out to sea. I don’t think that we can completely rule it out just yet.

Todd Gutner offers his thought later today. Enjoy the beginning of spring!